The present invention pertains to doppler radars including a transmitter which periodically transmits pulses of electrical energy and a receiver which receives reflected portions of the energy of the transmitted pulses and removes the carrier so that only the change of frequency is available. The signal which is provided by the receiver is referred to in the art as a bipolar video, or reflected, pulse train. In prior art range tracking apparatus the bipolar video pulse train is sampled by a circuit which is controlled by a range gate and the sampled signals are detected and filtered, after which they are used as part of an error signal in a conventional servo loop to control the position of the range gate. The major problem with this system is that the loop becomes unstable if the filter time constants are reduced too far. However, the large time constants of the prior art systems cause range errors which are largely dependent on the velocity or acceleration of targets. It is extremely difficult to design a servo loop which can accurately track wide variations of range, velocity and acceleration, such as missiles passing close to the radar vehicle. Further, the prior art systems are relatively complicated and expensive to produce.